Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01D—SEPARATION
  • B01D19/00—Degasification of liquids
  • B01D19/02—Foam dispersion or prevention
  • B01D19/04—Foam dispersion or prevention by addition of chemical substances
  • B01D19/0404—Foam dispersion or prevention by addition of chemical substances characterised by the nature of the chemical substance

Definitions

• the invention relates to an agent for defoaming liquid media, preferably aqueous solutions, which contains a defoamer oil and finely divided silica as active ingredients.
• DE-OS 24 43 853 describes a preparation which, according to its identification, consists of 0.2 to 7.5% by weight of highly disperse silica or highly disperse aluminum oxide and 95 . 5 to 99.8% by weight of a methylpolysiloxane-polyoxyalkylene block copolymer which contains 10 to 60% by weight of methylpolysiloxane and whose polyoxyalkylene block has more than 80 to 100% by weight of oxypropylene units.
• Preparations for defoaming aqueous solutions by dispersions are known from DE-OS 23 45 335, which are characterized by a content of 80 to 95% by weight of a mineral oil or vegetable or animal oil, 1 to 7.5% by weight. finely divided silica or finely divided aluminum oxide, 1.0 to 10% by weight of a methylpolysiloxane-polyoxyalkylene block copolymer which contains 10 to 60% by weight methylpolysiloxane and whose polyoxyalkylene block has 80 to 100% by weight oxypropylene units, and optionally 2 to 10 %
• nonionic emulsifiers which have an average HLB value of 8 to 14, the sum of the above-mentioned constituents having to be 100% by weight.
• Combinations of mineral oils, vegetable or animal oils and water-insoluble methylpolysiloxane-polyoxyalkylene block copolymers are used here as water-insoluble defoamer oils.
• the properties of the silica can be significantly influenced by a surface treatment.
• the partial hydrophobization of the silica can, however, also achieve opposite effects.
• DE-OS 21 07 082 teaches that a silica with a methanol number of 5 to 35 has an optimal balance between good flow properties and good compatibility with foams, in particular fire-fighting foams.
• the silica is used to fill and stabilize foams.
• the object of the present invention is to find a means for defoaming liquid media on the basis of defoamer oil and finely divided silica, the preparation being intended to meet various requirements: the defoaming action of the preparation should be superior to that of the prior art and it should can be distributed well in the medium to be defoamed, ie have the lowest possible viscosity.
• the defoaming agent based on defoamer oil, contains up to the same amounts of silica, which is at least partially hydrophobic and has a methanol number of 50 to 70, in particular a methanol number of 57 to 65.
• the methanol number is calculated using the following formula:
• the teaching according to the invention thus goes beyond specifying the use of hydrophobized silica as a means of improving the anti-foaming action of a defoamer oil and specifies a characteristic figure which characterizes the hydrophobicity of the silica.
• the fiction moderate defoaming agent on the one hand has a high effectiveness
• the other hand is so low viscosity that it can be easily distributed in the medium to be defoamed. If a silica with a lower methanol number is used, the viscosity of the preparation increases considerably. It is therefore possible to produce preparations with a high silica content.
• Defoaming agents according to the invention can therefore contain silica in amounts of up to 100% by weight, based on defoamer oil.
• Suitable defoamer oils are the defoamer oils known from the prior art, such as silicone oils, water-insoluble polysiloxane-polyoxyalkylene block copolymers, water-insoluble polyoxyalkylene glycols and their ethers, mineral oils, vegetable or animal oils.
• dimethylpolysiloxanes with a viscosity of 20 to 100,000 mPas are used as silicone oils.
• those polymers are preferred which contain 10 to 60% by weight of methylpolysiloxane blocks and the polyoxyalkylene blocks have 80 to 100% by weight of oxypropylene units.
• the water-insoluble polyoxyalkylene glycols or their ethers preferably have a molecular weight of 1500 to 2000.
• silica Precipitated or obtained by flame hydrolysis can be used as the silica.
• the silica is preferably rendered hydrophobic by the action of silanes or siloxanes on the silica at elevated temperatures in a manner known per se.
• hydrophobicize the silica by treatment with wax or wax solutions or dispersions.
• a further possibility for hydrophobizing is the treatment with silanes or siloxanes carrying fluorocarbon groups. ' The type of hydrophobization is different but not the subject of the present invention.
• Both the agents for hydrophobization and the hydrophobization processes are known from the prior art and, for example, in the . Book “Chemistry and Technology of Silicones" by W. Noll, Verlag Chemie GmbH, 2nd edition 1968, p. 369. Reference is also made to the published documents 21 07 082 and 28 29 906.
• Aw-bis (trimethylsiloxy) polydimethylsiloxane with a kinematic viscosity of 1000 mm 2 s -1 is used as defoamer oil.
• the preparations are produced using a glass vessel which has a useful content of 11 and is equipped with a cross-bar stirrer.
• the defoamer oil is presented.
• the required amount of the hydrophobized silica is incorporated while stirring at a peripheral speed of 2 ms-1.
• the mixture is stirred at 25 ° C. for a total of 60 minutes.
• Table 1 lists the compositions of the preparations and their viscosities, measured using the Haake Rotovisko plate and cone device at a shear rate of 54.2 s-1.
• an oil-free air stream is passed through 1000 ml of a 0.1% aqueous solution of a mixture of dodecylbenzenesulfonate and fatty alcohol polyglycol ether until 1000 ml of foam have formed.
• This air flow is introduced at a constant speed of 6 l / min through a glass frit of porosity 1.
• the air supply is interrupted by removing the frit from the measuring vessel.
• 50 mg of the defoamer preparation are added. After the foam has been completely destroyed, air is introduced again and the time measured for the renewed formation of a foam volume of 1000 ml.
• the mixtures described in Table 1 were converted into 10% emulsions.
• 10 parts by weight of the preparation and 2.5 parts by weight of a polyethylene glycol monostearate with a polyglycol content of approximately 60% by weight and 87.5% water were emulsified.
• the 50 mg of the defoamer preparation required to carry out the effectiveness test are contained in 0.5 ml of the emulsion described. This amount can be easily introduced into the measuring vessel using a micropipette.
• Example 1 The a-w-bis (trimethylsiloxy) polydimethylsiloxane described in Example 1 is used as defoamer oil.
• a precipitated silica which had been hydrophobicized with an aw-bis (trimethylsiloxy) polydimethylsiloxane and had a BET surface area of 100 m 2 / g and a methanol number of 65.2 was used as the hydrophobized silica.
• Table 2 lists the compositions of the preparations and their viscosities.
• the antifoam effect was determined in the manner described in Example 1.
• Example 1 was used as defoamer oil.
• the hydrophobic silica is a product obtained by flame hydrolysis product having a BET surface area of 20 0 m 2 / g which had been rendered hydrophobic with dimethyl polysiloxane and has a methanol number of 50.4.
• Table 3 shows the compositions of the preparations and their viscosities.
• Example 1 The oil mentioned in Example 1 is used as defoamer oil.
• the hydrophobized silica was obtained by treating a precipitated silica which has a BET surface area of 200 m 2 / g with methyltriethoxysilane. It has a methanol number of 30.5 which is too low compared to the methanol number of 50 to 70 required according to the invention.
• compositions of the are not invented preparations according to the invention and their viscosities.
• the defoamer preparation is prepared and tested in accordance with Example 1. However, a non-hydrophobicized silica was used. The results are summarized in Table 5.
• Table 6 The times obtained in the measurement of the defoaming effect of preparations according to Examples 1 to 5 until the formation of 1000 ml foam volume are summarized in Table 6. The measured values clearly show that the preparations according to the invention from Examples 1 to 3 are greatly superior to the preparations from Comparative Examples 4 and 5.
• Tables 1 to 5 teach that the preparations according to the invention from Examples 1 to 3 have low viscosities even at high levels of hydrophobized silica, which makes it much easier to process these preparations than with the very highly viscous preparations of the comparative examples.

Landscapes

• Chemical & Material Sciences (AREA)
• Health & Medical Sciences (AREA)
• Toxicology (AREA)
• Dispersion Chemistry (AREA)
• Chemical Kinetics & Catalysis (AREA)
• Degasification And Air Bubble Elimination (AREA)
• Compositions Of Macromolecular Compounds (AREA)

Applications Claiming Priority (2)

Publications (2)

Family

ID=6074180

Family Applications (1)

Country Status (2)

Cited By (3)

Families Citing this family (17)

Citations (10)

• 1979
  • 1979-06-26 DE DE19792925722 patent/DE2925722A1/de not_active Withdrawn
• 1980
  • 1980-04-10 DE DE8080101938T patent/DE3060961D1/de not_active Expired
  • 1980-04-10 EP EP80101938A patent/EP0023533B1/fr not_active Expired

Patent Citations (10)

Non-Patent Citations (1)

Also Published As

Similar Documents

Legal Events